05 Animal Nutrition #49 Diet The food an animal eat everyday is called diet. Most animals need 7 types of nutrients in their diet: carbohydrates, proteins, fats + water, fibre, vitamins, minerals. The amount of energy needed is provided mainly by our carbohydrate and fat intake. Your dietary requirements depend on your age, sex and activity. - Age: The energy demand increases until we stop growing. While children are growing they need more protein per kilogram of body weight than adults do. - Sex: Generally, males use up more energy than females. - Pregnant women need extra nutrients for the development of the fetus. A. A balanced diet is a diet that contains all the main nutrients in the correct amounts and proportions to maintain good health. B. Malnutrition is the result of not eating a balanced diet. There may be: wrong amount of food: too little or too much incorrect proportion of main nutrients lacking in one or more key nutrients Effects of malnutrition 1. Obesity - Too much food (carbohydrate, fat or protein) 2. Coronary heart disease Too much saturated/animal fat in the diet results in high cholesterol levels. Cholesterol can stick to the walls of arteries, gradually blocking them. If coronary arteries become blocked, the results can be angina and coronary heart disease. 3. Starvation Too little food can result in starvation. Extreme slimming diets, such as those that avoid carbohydrate foods, can result in the disease anorexia nervosa. Starvation 4. Childhood protein-energy malnutrition (Kwashiakor) Wrong proportion of nutrients e.g. too much carbohydrates (starchy foods) and a lack of protein can lead to Kwashiakor in young children. Kwashiakor characterized by edema, anorexia, ulcerating dermatoses. 5. Vitamin, mineral and fiber deficiency diseases - Lacking key nutrients. #50 Use of modern technology for increasing food production Modern technology such as chemical fertilisers, pesticides, herbicides, modern agricultural machinery, artificial selection... have been used to increase food production. - Development and use of chemical fertilisers on farm land à boots levels of nutrients in the soil, increasing crop yields. - Development and use of pesticides such as insectisides and fungicides à kill pests that feed on ar damage crops à increase crop yields. - Development and use of herbicides à kill weeds that compete with crops for nutrients, light, water and space à increase crop yields. - Use of modern machinery, such as tractors and combine harvesters à enables land and crops to be managed more efficiently. - Artificial selection to produce varieties of plants that are suited to particular climates and soil types, and breeds of animal for specific purpose such as optimum meat, milk, and wool production. - Use of medicines such as antibiotics, hormones and artificial insemination techniques in intensive animal rearing. - Use of plant hormones in plant growing and fruit production. - Use of genetic engineering and cloning techniques to produce organisms to produce hormones, etc. - Development of systems to water plants in greenhouses automatically and to grow plants in nutrient solutions (a process called hydroponics). - Use of satellites to monitor crop development, observe crop diseases and assess the need for additional fertiliser. - Development of intensive farming and automated feeding mechanisms. #51 Problems of world food supplies and the causes of famine There is not always enough food available in a country to feed the people living there. A severe food shortage can lead to famine. It has been calculated that more than enough food is produced on Earth to provide every single person with more than enough for their needs. Yet many people do not got enough food. Each year, many people die because they have an inadequate diet. The fundamental problem is that food is distributed unequally on our planet: while some parts of the world produce more than enough food for the people that live there, in other part of the world not enough food is produced. Although large amounts of food are transported from one area to another, this is still not sufficient to supply enough food to everybody. If food prices rise too high, many people may not be able to afford to buy it. Famine can occur for many different reasons: Climate change and natural disaster such as drought and flooding that prevent crops from growing. Increasing population: population may grow so large that the land on which they live can no longer provide enough food for them. Unequal distribution of food. #52 Human alimentary canal The alimentary canal is a long tube which stars at the mouth, runs through the stomach and intestines and finishes at the anus. It is part of the digestive system. The digestive system also includes the accessory organs (teeth, tongue, gallbladder, salivary glands, liver, the pancreas). Main regions of the alimentary canal and associated organs are: Mouth, salivary glands Oesophagus Stomach Pancreas, liver, gall bladder Small intestine (duodenum + ileum) Large intestine (colon +rectum) Anus. Food is broken down with the help of digestive juices, which contain special chemicals called enzymes. Functions of the regions of the digestive system: Common misconceptions The liver does not make digestive enzymes- bile is not an enzyme. It breaks fat down into smaller droplets, but does not change them chemically. The fat mollecules stay the same size, it is just the droplet size that changes from large to small due to the action of bile. Additional resource: classes.midlandstech.com #53 Human teeth and dental decay There are four types of teeth in human (incisors, canines, premolars and molars), each specialised for different funtions. Position of teeth in the mouth Structure of tooth Causes of dental decay - Bacteria are present on the surface of our teeth. Food deposits and bacteria form a layer called plaque. Bacteria on the plaque feed on sugars, producing acid. This acid dissolves enamel, forming a hole. - Dentine underneath the enamel is softer – it dissolves more rapidly. - If the hole reaches the pulp cavity, bacterial infection can get to the nerve. This results in toothache and possibly, an abscess (an infection in the jaw). Common misconceptions: Do not say that sugar causes decay. It only causes problems because of the activity of bacteria feeding on it and producing acids. Try this The outer layer of the crown of a tooth is resistant to attack by bacteria 1. Name this outer layer. (1 mark) 2. State the mineral and the vitamin needed in the diet for the healthy development of this layer. (2 mark) 3. Explain how bacteria can gain entry through this layer into the tooth and cause dental decay. (3 mark) Answers 1. Enamel 2. Mineral: calcium; vitamin: D 3. Three points from: bacteria feed on sugar from food left on the teeth bacteria produce acid acid attacks or dissolves the enamel dentine if softer, so it breaks down more quickly this results in a hole in the enamel, exposing the pulp cavity. #54 Adding fluoride to public water supplies Fluoride helps prevent destruction of the tooth surface caused by acids produced by bacteria. It forms a reservoir on the teeth from which fluoride is released during attack. It reduces the loss of minerals from the tooth and promotes repair of early tooth decay. Growing children can absorb fluoride in their diet (from toothpaste of fluoridated water). It becomes part of the enamel of their developing teeth, and the enamel; is then more resistant to tooth decay. Arguments for and against the addition of fluoride to public water supplies For: Tooth decay in the local population of children decreases. There is no need to buy fluoridated toothpaste. Against: It is form of mass medication – people have no choice about whether or not they want the treatment. Fluoride is a benefit only to growing children – adults do not benefit. If people take proper care of their teeth, fluoridation is unnecessary. Fluoride may have side effects, such as an increase in risk of bone cancer (but this is unlikely). Proper care of teeth Avoid sugary food, especially between meals, so bacteria cannot make acid and clean teeth regularly to remove plaque. Use dental floss or a toothpick to remove pieces of food and plaque trapped between them. Use fluoride toothpaste (or drink fluoridated water) – fluoride hardens tooth enamel. Visit a dentist regularly to make sure and tooth decay is reacted early and any stubborn plaque (called calculus) is removed. Common misconceptions There is a big difference between fluoride and fluorine. Fluorine is a very toxic gas, while fluoride is a mineral that helps to strengthen teeth. Make sure do not use the term fluorine in an exam answer about teeth. #55 Mechanical and chemical digestion Food that we ingest is mainly made up of large, insoluble molecules that can not be absorbed through the gut wall. It needs to be changed into small, soluble molecules. 1. Mechanical digestion is the physical process of preparing the food for chemical digestion. It involves chewing (in the mouth), mixing, churning (in the stomach and intestine) and segmentation (in the intestine). Large pieces of food are breaking down into smaller pieces à increases the surface area of the food. Bile physically digests fats by emulsifying them – turning them into small droplets with a large surface area. Chewing Mechanical digestion, performed bye the teeth à pieces of food are mixed with saliva and become smaller à easier to swallow and have a larger surface area. Peristalsis The walls of the alimentary canal have an inner, circular muscle fibre coat and an outer, longitudinal muscle fibre coat. As the ball of food (bolus) formed in the mouth enters the pharynx, a reflex action is initiated. This produces slow, wave-like contractions in the walls of the esophagus and later along the whole length of the tract (peristalsis). Peristaltic waves involve the contraction of the circular muscle fibres behind the bolus (A) and their relaxation in front of the bolus. Longitudinal muscles provide the wave-like action. The two functions together push the ball down the tract (B). Misconceptions: Chewing food does not involve breaking down large molecules into small molecules; it only breaks down large pieces into smaller pieces, giving a larger surface area for enzymes to work on. Video Peristalsis 2. Chemical digestion Involves breaking down large, insoluble molecules into small, soluble ones. Enzymes speed up the process. They work efficiently at body temperature (370C) and at suitable pH. The main places where chemical digestion happens are the mouth, stomach and small intestine. # 56 Absorption – function of small intestine and significance of villi Absorption is the movement of digested food molecules through the wall of the intestine into the blood or lymph. Digestion is completed in the small intestine. By now, most carbohydrates have been broken down to simple sugar, proteins to amino acids, and fats to fatty acids and glycerol. These molecules are small enough to pass through the wall of the small intestine and into the blood. This is called absorption. The small intestine is especially adapted to allow absorption to take place very efficiently. It has a very rich blood supply. Digested food molecules are small enough to pass through the wall of the intestine into the bloodstream. Water, mineral salts and vitamins are also absorbed in the small instestine. The small intestine absorbs 5-10 dm3 of water each day. How ever, the colon absorbs much less water and salt than the small intestine, generally around 0,3–0,5 dm3 per day. Significance of Villii Villi are finger like projections that increase the surface area for absorption. If a section of small intestine was turned inside out, its surface would be kike a carpet. Inside each villus are: - Blood capillaries: absorb amino acids and glucose. - Lacteals: absorb fatty acids and glycerol. Food molecules are absorbed: - mainly by diffusion. - or by active transport. Epithelial cells contain mitochondria to provide energy for absorption against the concentration gradient. Role of the hepatic portal vein The hepatic portal vein transports absorbed food from the small intestine to the liver. After a meal, the blood in this vein contains very high concentrations of glucose and amino acids, as well as vitamins and minerals. The liver reduces levels backs to normal. # 56 Absorption – function of small intestine and significance of villi Absorption is the movement of digested food molecules through the wall of the intestine into the blood or lymph. Digestion is completed in the small intestine. By now, most carbohydrates have been broken down to simple sugar, proteins to amino acids, and fats to fatty acids and glycerol. These molecules are small enough to pass through the wall of the small intestine and into the blood. This is called absorption. The small intestine is especially adapted to allow absorption to take place very efficiently. It has a very rich blood supply. Digested food molecules are small enough to pass through the wall of the intestine into the bloodstream. Water, mineral salts and vitamins are also absorbed in the small instestine. The small intestine absorbs 5-10 dm3 of water each day. How ever, the colon absorbs much less water and salt than the small intestine, generally around 0,3–0,5 dm3 per day. Significance of Villii Villi are finger like projections that increase the surface area for absorption. If a section of small intestine was turned inside out, its surface would be kike a carpet. Inside each villus are: - Blood capillaries: absorb amino acids and glucose. - Lacteals: absorb fatty acids and glycerol. Food molecules are absorbed: - mainly by diffusion. - or by active transport. Epithelial cells contain mitochondria to provide energy for absorption against the concentration gradient. Role of the hepatic portal vein The hepatic portal vein transports absorbed food from the small intestine to the liver. After a meal, the blood in this vein contains very high concentrations of glucose and amino acids, as well as vitamins and minerals. The liver reduces levels backs to normal. #57 Assimilation and role of the liver Assimilation is the movement of digested food molecules into the cells of the body where they are used, becoming part of the cells. Role of liver in the metabolism of glucose and amino acids Excess glucose in the blood arriving at the liver is converted into glycogen (animal starch) for storage, or broken down through respiration, producing energy for other purposes. Amino acids cannot be stored in our body, so any that is excess has to be dealt with in the liver. - Some amino acids are transaminated to produce a different amino acid. - The rest are deaminated to produce ammonia (NH3) and a keto acid. + NH3 is converted into urea, which is transported to the kidneys and excreted. + The keto acid is used primarily as energy for liver cells So Deamination is the removing of nitrogen-containing part of amino acids to form urea and using of the remainder of amino acid to provide energy to the liver cells. Role of liver in the breaking down of alcohol and other toxins Breaking down any toxins absorbed from the alimentary canal, including drugs such as alcohol. Cells in the liver are able to convert many toxins to harmless substances that can be transported in the blood and excreted from the body. Role of fat as an energy storage substance Fatty acids and glycerol pass into the lymphatic system and then the bloodstream. Once in the blood nutrients are carried to all cells of the body. Some are oxidised to produce energy and others are used to repair the cell, build new cells. Fat is a good storage compound – it releases twice as much energy as carbohydrates when respired, and act as insulation in the skin. Some nerve cells form a myelin sheath from fat, to prevent electrical impulses from leaking out. #58 Summary of animal nutrition A balanced diet contains suitable proportions of each group of nutrients – carbohydrates, fats, proteins, minerals, vitamins, water and fibre – and the correct amount of energy. Eating food containing more energy than you can use up causes weight increase, which can lead to obesity. Children who do not get enough food may suffer from energy protein malnutrition, in which they do not grow properly and have little energy. Digestion is the breakdown of large molecules of food into small ones, so that they can be absorbed through the wall of the alimentary canal. Mechanical digestion breaks down large pieces of food to small ones. It is done by the teeth, the muscles in the wall of the alimentary canal and bile salts. Chemical digestion breaks down large molecules to small ones. It is done by enzymes. Mammals have four types of teeth – incisors, canines, premolars and molars – each with their own functions. Digestion begins in the mouth, as teeth grind food into smaller pieces, and amylase digests starch to maltose. Protein digestion begins in the stomach, where pepsin digests proteins to polypeptides. Rennin is present in young mammals, and clots milk protein. Hydrochloric acid kills bacteria and provides a low pH for the action of pepsin. Pancreatic juice flows into the duodenum. It contains enzymes that digest starch, proteins and lipids, and also sodium hydrogencarbonate to partly neutralise the acidity of food coming from the stomach. Bile also flows into the duodenum. It contains bile salts, which emulsify fats, making it easier for lipase to digest them. The lining of the small intestine is covered with villi, giving it a very large surface area, which helps to speed up absorption. Cells on the surface of the villi make enzymes, which complete the digestion of food. The villi contain blood capillaries to absorb glucose, amino acids, water, vitamins and minerals, and lacteals to absorb fatty acids and glycerol. The absorbed nutrients are carried to the liver in the hepatic portal vein. Some are used in the liver, some are stored, and some are sent on in the blood to be delivered to cells all over the body. The colon absorbs more water from the food. In the rectum, the undigested food is formed into faeces, which are eventually egested through the anus.
